Endocrine studies in ivermectin-treated heifers from birth to puberty.

Abstract

Continuous treatment with ivermectin from birth to puberty advanced sexual maturation by 3.7 wk in Holstein heifers grazing pastures naturally infected with nematodes. Every 14 d jugular blood samples were taken from birth to 45 wk of age from all heifers. No differences in serum FSH, estradiol, or thyroxine levels were observed during the trial between the treated and untreated group. Mean LH levels were diminished in untreated heifers 4 wk before the first estrus and the amplitude of LH pulses was augmented in treated heifers when puberty was reached. Serum IGF-I levels increased from birth to 22 wk of age and then reached a plateau in both groups, but levels were consistently higher in treated heifers from 26 wk of age onward. Body weight gain was retarded in parasitized heifers and IGF-I values were positively correlated with body weight only during the first 20 wk of life. We suggest that enhanced prepubertal IGF-I levels in conjunction with increased prepubertal LH levels and pubertal LH pulse amplitude might be involved in the accelerated somatic maturation and in puberty advancement observed in ivermectin-treated heifers.

Gastrointestinal parasite control during prepuberty improves mammary parenchyma development in Holstein heifers

“…Furthermore, parasites in cows during the periparturient period were related to impaired milk production (Perri et al, 2011). The effects of gastrointestinal parasites, both on development and production itself, were associated with altered profiles of circulating metabolic hormones (Lacau-Mengido et al, 2000Díaz-Torga et al, 2001;Perri et al, 2011). Maximal levels of IGF-1 reached during prepuberty were lower in untreated than in ivermectin treated heifers (Lacau-Mengido et al, 2000) and time of prepubertal increase in serum leptin levels was delayed in untreated heifers (Díaz-Torga et al, 2001).…”

“…The IGF-1 RIA was performed after acid-ethanol extraction as described in Lacau-Mengido et al (2000). The IGF-1 antibody (UB2-495) of the NIDDK was used.…”

“…The effects of gastrointestinal parasites, both on development and production itself, were associated with altered profiles of circulating metabolic hormones (Lacau-Mengido et al, 2000Díaz-Torga et al, 2001;Perri et al, 2011). Maximal levels of IGF-1 reached during prepuberty were lower in untreated than in ivermectin treated heifers (Lacau-Mengido et al, 2000) and time of prepubertal increase in serum leptin levels was delayed in untreated heifers (Díaz-Torga et al, 2001). In adult lactating cows, diminished milk production in cows with positive nematode egg counting in feces around parturition was associated with decreased prolactin, GH, and IGF-1 levels (Perri et al, 2011).…”

Dehydroepiandrosterone treatment attenuates oestrogen-induced pituitary hyperplasia

“…For IGF-I RIA serum samples (15 µl) and standards were subjected to the acid-ethanol cryoprecipitation method as previously described (Lacau-Mengido et al 2000). IGF-I was determined using an antibody (UB2-495) provided by Drs L Underwood and J J Van Wyk, and distributed by the Hormone Distribution Program of the NIDDK.…”

Change in Circulating Follicle-Stimulating Hormone, Luteinizing Hormone, Immunoreactive Inhibin, Progesterone, Testosterone and Estradiol-17.BETA. in Fillies from Birth to 6 Months of Age

“…The e n d o c r i n e m e c h a n i s m s c o n t r o l l i n g o v a r i a n development and sexual maturation are also becoming clear [14]. Endocrinological studies on several species have found that follicular growth correlates with serum concentrations of follicle stimulating hormone (FSH), which together with luteinizing hormone (LH), gradually increases from birth to puberty [9,11]. Recent studies in heifers and rats have shown that an increase in FSH and LH in neonatal calves activated follicular growth in the ovaries [6,11,14], that an increase in FSH induced new follicular growth in a wave-like manner in neonatal calves, and that the growing stage of follicles with the ability to secrete of estradiol gradually progressed until puberty [11,14].…”